A window covering of the kind that is of particular interest here consists of a textile fabric or a pliable plastic material which is formed into a plurality of parallel pleats, and which on raising or lowering the material folds and unfolds along the pleat lines. In the usual situation, the wall portion to be covered is substantially rectangular so that the wall covering itself is rectangular and readily moved vertically between open and closed positions in conventional manner.
There are many situations in which a window, for example, has an upper edge which is arranged at an angle to the horizontal, or other situations where the ceiling may be canted at an angle so that a wall covering to conform to a space to be covered must have an upper edge that is similarly arranged at an angle to the horizontal. Such a wall covering is frequently referred to as an "A-frame" covering and when the term is used herein it will be in that sense.
An A-frame wall covering, since it has an upper edge that is angularly disposed to the horizontal, can only be raised to the lowermost end of the angled upper edge. Moreover, the portion of the covering or blind between the two ends of the angled edge remain in extended position throughout use which presents a difficult fabrication problem in securing the angled cut edge of the covering fabric to the angularly disposed head rail to which the covering is attached without puckering, tearing or otherwise distorting the material. In the past, interconnections between the fabric portion of the covering to the angularly disposed headrail have been a relatively difficult hand operation which frequently resulted in a puckered interconnection point or series of points that were both unsightly and not fully reliable.